Compressor



Nov. 4, 1952 J. NAAB COMPRESSOR Filed June 25, 1948 Patented Nov. 4, 1952 COMPRESSOR Julius Naab, Easton, Pa., assignor to Ingersoll- Rand Company, New York, N. Y., a corporation of New Jersey Application June 23, 1948, Serial No. 34,712

3 Claims. 1 This invention relates to compressors, and more particularly to unloaders for multi-stage compressors.

One object of my invention is to completely unload a multi-stage compressor in a relatively simple and automatic manner.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings accompanying this specication and in which similar reference numerals refer to similar parts,

Figure 1 is an end view, partly in section, of a two-stage compressor embodying the present invention,

Figure 2 is a transverse view taken through Figure 1 along the line 2-2,

Figure 3 is a transverse view taken through Figure 2 along the line 3--3 and shows the construction of a valve means for controlling communication between the inlet and clearance pockets of the second stage compressor, and

Figure 4 is a view through Figure 1 along the line 4-4 and shows the by-pass valve arrangement for the low pressure stage.

Referring to the drawing, number I designates, in general, a two-stage variable capacity compressor provided with clearance valves II and that control the output, or capacity, of the low pressure stage I5 and high pressure stage I 6, respectively. The valves I I and III, are actuated by pressure fluid supplied thereto through conduits 2|2 and 3|2, respectively, connected to a conventional regulator I2. The regulator I2, in turn, is supplied pressure fluid from a source, such as a receiver (not shown) for the compressor discharge, and is connected by a conduit |I2 to a point (not shown) in the uid system and is responsive to variations in pressure at such point to control the compressor output in a conventional manner Further control over the unloading of the compressor is provided by means of by-pass valves I3 and I4 adapted respectively to the low and high pressure stages I5 and IB of the compressor. The valves I3 and I4 cooperate in such a manner that pressure fluid in the high pressure stage may be by-passed through an intercooler I1, connected in series between the two stages-that is, between the outlet of one cylinder and the inlet of the preceding cylinder,

and thence through the low pressure stage I5 to |`8 and IIB and discharge valves I9 and ||3 in-4 the outer periphery of the opposite end portions of the associated cylinders and |20. Both cylinders 20 and |20 denne compression chambers 2| and |2| for the reciprocative pistons 22 and |22 for the low pressure stage I5 and the high pressure stage I6, respectively. The cylinders 20 and |20 are further provided with a water jacket 23 and |23. respectively, around the intermediate and at the end portions thereof.

Encircling the high pressure cylinder |20 is a housing |24 that cooperates with the cylinder |20 to form a chamber which is subdivided by outwardly extended support or rib members |25 and |26 that, respectively, encircle and extend longitudinally of the cylinder |20 to form clearance pockets |21 and inlet and outlet passages |28 and |29, respectively, for the compressor. In this respect the high and low stages are similar. Accordingly the low pressure stage I5 is provided with a housing 24 dening a chamber which is subdivided by ribs 25 and 25 forming clearance pockets 21 and inlet and outlet passages 28 and 29, respectively. In the low pressure stage an additional member 30 extends partially around the cylinder 20 and cooperates with the housing 24 and the member 23 to form a by-pass passage 3| that communicates the inlet 28 and outlet 29 of that stage.

In this instance there are two clearance pockets 21 and |21 positioned at each end of the associated cylinder, 20 or |20 which are communicated with the compression chambers 2| and IZI, through ports 32 and |32; respectively. It is through these ports 32 and |32 that the flow of pressure fluid is controlled by the clearance valves I and I I mounted in the housings 24 and |24, respectively. With this arrangement a stepby-step unloading of the compressor is available, and, in order to accomplish complete unloading, at least one clearance pocket |21 at each end of the housing |24 of the high pressure stage |6 is communicated with the inlet passage I 28 thereof through the by-pass valve |4 mounted in the support member |26. This arrangement in cooperation with the passage 3|, provides a ilow path for reverse flow of fluid from the high pressure cylinder to the inlet side of the low pressure cylinder whenever the by-pass valve I4 and the clearance valve associated therewith are both open.

Automatic control is maintained over the complete unloading of the high pressure stage I6 of the compressor through the means provided for controlling the communication between theclea're.

ancepockets |21 and the inlet |28, of the high pressure stage I6, in response to variations in pressure in the inlet |28, or intercooler I1; and to this end, the 'uid pressure operated valves I4 are designed to be actuated by the uid, the flow of which they control and are mounted in the housing |24 in such a manner as to be exposed to the pressure diierential between the clearance pockets |21 and the inlet |28. As shown, each of the valves I4 comprise a tubular member 33 having a recess 34 therein for the reception of the valve member 35. The member 35 is provided with heads 36 and 31 at the opposite ends thereof and the inner, with respect to the housing |24, head 36 resides in an enlarged portion 38 of the recess 34. The material forming the outer end of the enlarged portion 38 is tapered to form an annular seat 39 which cooperates with a complementary surface on the head 36. This seat area, or complementary surface, on the head 33 is exposed to pressure fluid in pocket |21 whenever the head 36 moves from its seat, thereby increasing the area of pressure surface exposed for actuating the valve member 35 into the open position, and snap action of the valve occurs.

Positioned, respectively, inwardly and outwardly of the seat 39 are holes 46 and 4I in the tubular member 3. With this construction communication between the holes 40 and 4I is controlled by the action of the Valve member 35 which, in this instance, is actuated outwardly against the seat 39 to cut-off communication between the holes 40 and 4| by the action of uid pressure on the inner end surfaces of the heads 36 and 31, and is actuated inwardly into the open position by uid pressure on the outer surface of the head 3S and by means of a spring 42 interposed between the head 31 and the material forming the outer end of the recess 34. The outer end of the recess 34 is exposed to the atmosphere through a vent 43 in order to permit free movement of the member 35 in the recess. As best shown in Figure 3, the Valves I4 are mounted in the support members |26 in such a manner that the outer holes 4I are exposed to the clearance pockets |21 and the inner holes 4S are exposed to the inlet |28 of the high pressure cylinder; thus the valves I4 serve as a means for controlling communication between the clearance pockets |21 and the inlet |28 in accordance to predetermined pressure variations existing in the inlet |28.

The valve I3 that cooperates with the valve I4 to completely unload the compressor, is mounted in thehousing of the low pressure stage I and serves as a means for controlling the iloiv of air through the passage 3| that communicates the inlet and outlet of that stage by controlling the now or" fluid through an opening 44 in a member 45 positioned across the passage 3|. As arranged, the valve I3 is held in the open position by means of a spring 46 and is biased in the closed position by the action of the pressure uid delivered thereto through a conduit 41 connected in the regulating device I2. The Valve I3 is, in this instance, actuated into the open position to completely unload the low pressure cylinder whenever the pressure in that part of the ud system (not shown) in which the regulating device I2 is connected, reaches the predetermined value at which the regulator I2 exhausts the pressure fluid from the conduit 41. Subsequently the high pressure cyinder will be unloaded through the intercooler I1 in that the communication of the inlet 28 with the outlet 23 of the 10W pressure stage necessarily causes the pressure to drop in the intercooler I1, which in turn causes a drop in pressure in the inlet |28 of the high pressure stage. The latter drop in pressure permits the spring 42 to bias the valve member 35 into the open position and thereby establish communication between the clearance pockets |21 of the high pressure stage and the outlet 23 of the low pressure stage.

The valves II and III may be of any conventional air operated type clearance valve. By way of illustration these valves may be similar in construction and operation to the valve I3. Accordingly whenever the regulator I2 exhausts pressure uid from a clearance valve, the valve is unseated to communicate the associated clearance pocket with the compression chamber to partially unload the compressor. Conversely whenever the regulator valves uid to the clearance valve, it is seated to cut off such communication and load the compressor.

Under normal operating condtions the by-pass valves I3 and I4 are held in the closed position and the regulator I2 controls the operation of the clearance valves I I in the usual manner. In the event that the demand on the compressor is such that complete unloading of the compressor is desirable, the pressure uid is exhausted from the regulator by either a manually operated or automatic means, not shown, and the regulator I2 will in turn exhaust pressure i'luid from the by-pass Valve I3 and the clearance Valves II so that the pressure in the intercooler I1 immediately drops to a value at which the by-pass I4 is actuated into the open position and any iluid in a high or low pressure cylinder is exhausted to the inlet or suction side of the low pressure stage. On starting the compressor, pressure is built up in the uid system and the regulator I2 closes the clearance control valves II and the low pressure by-pass valve I3 so that pressure is built up in the intercooler I1 t0 a point where the pressure on the surface of the inner end oi the head 36, moves the valve member 35 inwardly against the pressure of the spring 42 and closes the valve I4. The compressor is now in condition to operate in the usual manner.

It is now obvious that the present invention provides a simple and effective means for completely and automatically unloading the high pressure stage of a compressor in cooperation with the unloading means for the initial, or low pressure, stage. This, in starting the compressor, reduces the starting torque on the prime mover, such as a synchronous motor, by relieving the pressure on the compressor piston; and prevents whipping of the piston and undue strain in the prime mover due to the compression and expansion of fluid trapped in the high and low pressure cylinders when the compressor is being shut down. The automatic feature of the high pressure by-pass valve I4 also eliminates any need for external piping and permits the valve I4 to be adapted wholly within the housing |24.

While I have shown and described a specific form of my invention it is to be understood that various changes and modications may be made without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. The combination with a multi-stage compressor having a pair of cylinders connected in series and inlets and outlets and clearance pockets for the cylinders, of an unloader comprising means communicating the clearance pockets and the inlet of one of the cylinders, pressure responsive means for controlling the communication between said clearance pockets and inlet, said means being actuated by pressure fluid in the inlet of the cylinder to which it is adapted, means for communicating the inlet with the outlet of the other cylinder, and means for controlling communication established by the last said means.

2. The combination with a multi-stage compressor having a plurality of cylinders with inlets and outlets and clearance pockets therefor, connecting means for communicating the inlet of one cylinder with the outlet of the cylinder of the preceding stage, comprising means for communicating the clearance pockets With the inlet of the associated cylinder for all but the initial stage, means for controlling the last said communication, the last said means being responsive to pressure variation in the inlet of the cylinder with which it is associated, means for communicating the inlet with the outlet of the initial stage, and means for controlling communication established by the last said means.

3. The combination of a multi-stage compressor having high and low pressure stages, cylinders for the high and low pressure stages having inlets and outlets for pressure fluid,

housings for said cylinders, clearance pockets for said cylinders, means for directly communi cating the inlet and the clearance pockets of the high pressure stage, valve means Within the housing for the high pressure stage for automatically controlling said communication ben tween the clearance pockets and the inlet, said valve means acting responsively to the uid pressure in the inlet of the high pressure stage, means for communicating the inlet with the outlet of the low pressure stage, valve means for controlling said communication for the low pressure stage, and means for controlling the operation of the last said valve means.

J ULIUS NAAB.

REFERENCES CITED The following references are of record in the le of this lpatent:

UNITED STATES PATENTS Number Name Date 685,704 Wilkinson Oct. 29, 1901 1,614,143 Metzgar Jan. 11, 1927 1,636,439 Riesner July 19, 1927 1,969,076 Hirsch Aug. 7, 1934 2,165,938 Noble July 11, 1939 

